1. Field of the Invention
The present invention relates to a contour measuring apparatus, e.g., a three-dimensional measuring apparatus for outputting three-dimensional data representative of an object by a sinusoidal phase lattice method. More particularly, the present invention relates to a device for driving a lattice film included in the three-dimensional measuring apparatus or similar light transmitting member that transmits light issuing from a light source in order to project a stripe pattern on the surface of an object.
2. Description of the Background Art
A sinusoidal phase lattice method is applicable to a three-dimensional measuring apparatus for accurately obtaining three-dimensional data representative of a desired object. Specifically, the method illuminates an object such that a stripe pattern is projected on the object and causes a camera to shoot the object. The stripe pattern is sequentially moved in, e.g., the vertical direction, so that the camera shoots the object at a plurality of points, e.g., four points. Subsequently, another camera shoots the same object at four points, but in a different direction. The resulting image data output at eight points in total are processed to produce three-dimensional data relating to the object.
A conventional three-dimensional measuring apparatus includes two camera and projector assemblies spaced from each other by a suitable distance. Each camera and projector assembly has an optical axis directed toward the center. An object to be measured is positioned at the center between the camera and projector assemblies. The projectors each include a lattice film or light transmitting member for projecting a stripe pattern on the object, a driving device for moving the lattice film in order to shift the position where the stripe pattern is projected on the object, and a shutter for screening the stripe pattern output from the lattice film.
A prerequisite with the conventional measuring apparatus described above is that each projector projects an accurate stripe pattern on the surface of the object for accurate measurement. Another prerequisite is that the lattice film and therefore the stripe pattern be accurately moved at preselected intervals. However, the conventional measuring apparatus, particularly the driving device included therein, is sophisticated in configuration and needs a number of parts, which increase the cost. Moreover, the accuracy of displacement of the lattice film available with the driving device is short.
It is an object of the present invention to provide a driving device included in a three-dimensional measuring apparatus or similar contour measuring apparatus and capable of moving a lattice film or similar light transmitting member accurately to a preselected position.
It is another object of the present invention to provide a simple, low-cost driving device for driving a light transmitting member included in a three-dimensional measuring apparatus or similar contour measuring apparatus.
A three-dimensional measuring apparatus or similar contour measuring apparatus of the present invention includes a projector for emitting light, a lattice film or similar light transmitting member, and a camera. Light issuing from the projector is transmitted through the lattice film to illuminate an object to be measured. The lattice film is movable to a plurality of projecting positions in a preselected direction. The camera shoots the object being illuminated by the light. A driving device for driving the lattice film includes a cam follower associated with the lattice film, and a cam for guiding the cam follower. The cam has a cam surface including a plurality of contiguous, insensitive portions each for causing the lattice film to remain in a halt at a particular position when the cam follower contacts the insensitive portion.